If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Quick update:
I upgraded to Ubuntu 18.04LTS and also installed kernel 4.17rc3. Then I white-listed AMDGPU and configured grub to use it again. The system is rock solid. I left it several times alone to go idle and it didn't freeze. It also successfully shut down both monitors when it had to (It used to hang while trying to do this).

Thanks!

UPDATE: check posts below. It freezed again, and I had to upgrade the BIOS to get a new setting and fix it there.

Comment

I don't know if this will help, but I've experienced a similar system lockup with my R7 260x and AMDGPU and not with Radeon (processor is Dual Xeon X5687). What was causing my lockups was the "Lock the screen when going to sleep" tick box in the XFCE Power Manager. Unticked that and my desktop is working great again. That's not a good solution if your PC is somewhere public. I'm the only person who uses my PC or who has access to it so it's just fine for me. I'm not sure if it's a Light Locker, AMDGPU, or XFCE bug, but I know how to trigger it -- let it idle, blank, security kicks in, and then wait more than 20 mins...if it just kicks in and I catch it, it doesn't freeze up, but if it sits for more than 10 or 20 mins, it'll freeze up.

What sucks is I'm having such great results with gaming on AMDGPU these days that I'd rather deal with this bug versus switch drivers.

Comment

What was causing my lockups was the "Lock the screen when going to sleep" tick box in the XFCE Power Manager.

The Xfce power manager and screensavers can cause freeze, i noticed that several months ago. The xorg server has dpms built in, my screen blanks in 30 minutes or so without the xfce power manager and a screen saver installed. My system wakes ups nicely. You can control dpms with xorg.conf, see Arch Linux wiki.

Comment

The Xfce power manager and screensavers can cause freeze, i noticed that several months ago. The xorg server has dpms built in, my screen blanks in 30 minutes or so without the xfce power manager and a screen saver installed. My system wakes ups nicely. You can control dpms with xorg.conf, see Arch Linux wiki.

I'm using LXDE, but it has exactly the same problem and had to do the same workaround before.

About this issue: I used 4.17rc3 for a few weeks, and I no longer saw the hangs while going idle and turning off the screens. However, I got random lockups and no panic messages. Even REISUB didn't work. So I went back to my reliable fix: blacklist AMDGPU and use radeon only. It's very disappointing, but it's the only thing that seems to work. The power management does work OK with the radeon module. From what I remember when I started with this thread, the fix only works while AMDGPU is completely blacklisted and it hangs if it's loaded, even if it's not in use.

All I can say is:
1) Update your motherboard BIOS, and search for a setting like this: "Typical Current Idle". Make sure you change it to ON (do not leave it in "Auto". It must be manually enabled)
I have a Gigabyte motherboard, and the setting can be found here:
M.I.T->
Advanced Frequency Settings ->
Core Settings ->
*Power Supply Iddle Control = Typical

The names can be different from one motherboard brand to the other.

2) Edit /etc/modprobe.d/blacklist.conf and add "blacklist amdgpu" to the bottom. After that run "sudo update-initramfs -u -k all". This way you will make sure it won't be loaded.

I was able to ahve a 100% reliable system by doing those two steps. The first step "fixes" this very public and widespread bug: https://bugs.launchpad.net/ubuntu/+s...x/+bug/1690085
The second step (I think) is related to the power management with AMDGPU on some cards (I own an AMD 390x, which is GCN 1.1). I'm going to enable AMDGPU again right after they release kernel 4.19, which is supposed to have new power management features (and I hope they fixed this bug as a side effect)